Researchers from the Milá y Fontanals Institution (IMF) and the Institute of Archaeology (IAM) of the Spanish National Research Council (CSIC), together with scientists from the Museum of Human Evolution (MEH), the Faculty of Veterinary Medicine of the University of Extremadura (UEx), the UCM-ISCIII Joint Centre for Human Evolution and Behaviour in Madrid, the Laboratory of Prehistoric Archaeology of the University Jaume I of Castellón (UJI) and the Faculty of Geological Sciences of the Complutense University of Madrid (UCM) have participated in the largest genetic study carried out to date, which has made it possible to determine that the horses from which all current domestic horses descend were first domesticated in the steppes north of the Caucasus and, from there, spread to other regions of Asia and Europe.
This study brings to an end a long-standing debate about the location and chronology of the earliest documented evidence of domestication of the horses that gave rise to today’s populations, as well as aswering questions about when this domestication process began to spread to other regions of the world, thus replacing other types of horses that existed at the time. The results have been published in the October issue of prestigious international journal Nature.
This conclusion was reached by a team of 114 institutions and 162 researchers specialising in archaeology, palaeogenetics and linguistics, led by Professor Ludovic Orlando, CNRS researcher and principal investigator of the ERC-PEGASUS project, which, together with France Genomique-Projet Bucéphale, financed the research. The study involved sequencing the genomes of 273 remains of horses that inhabited various regions of Eurasia in a chronological arc extending from 50,000 to 200 BC. All the genetic information was sequenced at the Centre for Anthropobiology and Genomics of Toulouse, CAGT (CNRS/University of Toulouse III-Paul Sabatier) and Genoscope (CNRS/CEA/University of Évry), before being compared to the genomes of modern domestic horses. Thanks to the large battery of statistical analyses carried out, it has been possible to establish that between 2,200 and 2,000 BC, a drastic change took place in which the genetic profile existing in the Pontic steppes began to spread beyond its region of origin, thus replacing in a few centuries all wild horse populations from the Atlantic to Mongolia.
According to L. Orlando, «this replacement in the genetic composition of Eurasian populations is associated with significant genomic differences between this new type of horse and the horses of the populations that disappeared. On the one hand, this new type of horse from the steppes of the northern Caucasus had a more docile behaviour and, on the other hand, a more robust constitution in the vertebral skeleton». The researchers suggest that these characteristics triggered the successful selection of these animals, at a time when horse travel was becoming widespread in Eurasia.
According to Pablo Librado (CNRS), first author of this research, «this study has also shown that the distribution of this new type of horse in Asia coincides with the appearance of light carts and the spread of Indo-Iranian languages. In contrast, the migration of Indo-European populations from the steppe zone to the heart of Europe during the third millennium BC did not use this new type of horse as a vector for its expansion. This result demonstrates the importance of also incorporating the genetic history of animals when analysing the dimension of human migrations and intercultural contacts».
The individuals analysed include equids from various sites on the Iberian Peninsula, including Casas del Turuñuelo (Guareña, Badajoz) and Cova Fosca (Alt Maestrat, Castelló).
The Cova Fosca was excavated by Francesc Gusi and Carmen Olaria. According to C. Olaria, professor of Prehistory at the UJI and co-author of this study, «Cova Fosca has a very rich Holocene archaeozoological record. We were able to identify horse remains in ancient Neolithic levels, a very rare taxon in Iberian sites from this period. This uniqueness allowed us to publish years ago, together with Jaime Lira Garrido and Juan Luis Arsuaga, the first mitochondrial sequences of horses from this site». According to J. L. Arsuaga, scientific director of the Museum of Human Evolution, professor of Palaeontology at the UCM, director of the UCM-ISCIII Joint Centre and co-author of this study, «in Cova Fosca we found a unique mitochondrial lineage exclusive to Iberia that currently appears in very few horses, all of which are Iberian or of Iberian origin. In this new study we aimed to unveil the genomic secrets of the Cova Fosca».
Building Tartessos and Casas del Turuñuelo
Casas del Turuñuelo is one of the most impressive discoveries in peninsular archaeology in recent years. Its excavations are being carried out under a project directed by the IAM-CSIC and are being co-directed by Esther Rodríguez González and Sebastián Celestino, also researchers at the IAM-CSIC. According to Esther Rodríguez González, co-author of this new study, «Turuñuelo is an architectural complex from the middle of the first millennium BC belonging to the Tartessos culture where we have found the largest hecatomb documented to date in a site of Mediterranean protohistory. This mass slaughter is notable for the large number of equids that have been differentiated in the courtyard of this site. For this study we selected Equid 4». According to Sebastián Celestino, also co-author of this research, «a multidisciplinary team of specialists from the humanities and biosciences has been created around Turuñuelo, which is generating a constant exchange of information and ideas, thus offering a great multidisciplinary approach to the study of this site».
Among the lines of research of «Construyendo Tartessos» [Building Tartessos], the genetic study of these slaughtered equids stands out. Jaime Lira Garrido (UEx/Centro Mixto UCM-ISCIII), who is a co-author of this study, explains that «this latest work led by Professor Orlando has also allowed us to delve deeper into the evolutionary history of Iberian horses. In a previous study, Orlando and his team discovered that a genomic lineage developed on the Iberian Peninsula that is now extinct and very different from the rest of the ancient and modern Eurasian horse lineages described to date. The evolutionary origin of this lineage and the causes that led to its disappearance are still unknown. However, we have been able to identify in the Neolithic sample from the Cova Fosca the oldest evidence of this extinct lineage and that the Turuñuelo Equid 4 was, nevertheless, a descendant of this new type of horse that was so rapidly distributed throughout the known world some 4.000 years ago».
This study has been funded mainly by the European Research Council (PEGASUS project) and France Genomique (Bucéphale project).
Librado, P., (…), Orlando, Ludovic (2021). «The origins and spread of domestic horses from the Western Eurasian steppes». Nature, 20/10/2021.